What makes the diesel revival possible are advances in systems that can reduce tailpipe emissions, which are generally higher for diesel than for gasoline engines. Those systems work by combining the fuel with an additive that reduces emissions of nitrogen oxide, one of diesel engines’ main and most harmful byproducts.
“The fallout could be a black eye for a technology that had been making a lot of progress over the last few years,” said Don Anair, deputy director in the clean vehicles program at the Union of Concerned Scientists.